dma: contiguous: Turn heap registration logic around

The CMA heap instantiation was initially developed by having the
contiguous DMA code call into the CMA heap to create a new instance
every time a reserved memory area is probed.

Turning the CMA heap into a module would create a dependency of the
kernel on a module, which doesn't work.

Let's turn the logic around and do the opposite: store all the reserved
memory CMA regions into the contiguous DMA code, and provide an iterator
for the heap to use when it probes.

Signed-off-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Link: https://lore.kernel.org/r/20260331-dma-buf-heaps-as-modules-v4-1-e18fda504419@kernel.org

1 files changed, 5 insertions, 0 deletions

diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h
index 60b63756df82..c4c93c72ff6f 100644
--- a/include/linux/dma-map-ops.h
+++ b/include/linux/dma-map-ops.h
@@ -99,6 +99,7 @@ static inline struct cma *dev_get_cma_area(struct device *dev)
 		return dev->cma_area;
 	return dma_contiguous_default_area;
 }
+struct cma *dma_contiguous_get_area_by_idx(unsigned int idx);
 
 void dma_contiguous_reserve(phys_addr_t addr_limit);
 int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
@@ -117,6 +118,10 @@ static inline struct cma *dev_get_cma_area(struct device *dev)
 {
 	return NULL;
 }
+static inline struct cma *dma_contiguous_get_area_by_idx(unsigned int idx)
+{
+	return NULL;
+}
 static inline void dma_contiguous_reserve(phys_addr_t limit)
 {
 }